Research Reports - Sex differences in working memory after mild traumatic brain injury

Purpose To evaluate sex differences in mild traumatic brain injury (MTBI) with
working memory functional magnetic resonance (MR) imaging. Materials and Methods
Research ethics committee approval and patient written informed consent were
obtained. Working memory brain activation patterns were assessed with functional
MR imaging in 30 patients (15 consecutive men and 15 consecutive women) with MTBI
and 30 control subjects (15 consecutive men and 15 consecutive women). Two
imaging studies were performed in patients: the initial study, which was
performed within 1 month after the injury, and a follow-up study, which was
performed 6 weeks after the first study. For each participant, digit span and
continuous performance testing were performed before functional MR imaging.
Clinical data were analyzed by using Kruskal-Wallis, Mann-Whitney U, Wilcoxon
signed rank, and Fisher exact tests. Within- and between-group differences of
functional MR imaging data were analyzed with one- and two-sample t tests,
respectively. Results Among female participants, the total digit span score was
lower in the MTBI group than in the control group (P = .044). In initial working
memory functional MR imaging studies, hyperactivation was found in the male MTBI
group and hypoactivation was found in the female MTBI group compared with control
male and female groups, respectively. At the 6-week follow-up study, the female
MTBI group showed persistent hypoactivation, whereas the male MTBI group showed a
regression of hyperactivation at visual comparison of activation maps. The male
MTBI group was also found to have a higher initial ß value than the male control
group (P = .040), and there was no significant difference between the male MTBI
group and the male control group (P = .221) at follow-up evaluation, which was
comparable to findings on activation maps. In the female MTBI group, average ß
values at both initial and follow-up studies were lower compared with those in
the female control group but were not statistically significant (P = .663 and P =
.191, respectively). Conclusion Female patients with MTBI had lower digit span
scores than did female control subjects, and functional MR imaging depicted sex
differences in working memory functional activation; hypoactivation with
nonrecovery of activation change at follow-up studies may suggest a worse working
memory outcome in female patients with MTBI.